Recombinant production of two xylanase-somatostatin fusion proteins retaining somatostatin immunogenicity and xylanase activity in Pichia pastoris.

Somatostatin (SS) is one of the peptide hormones that regulate the endocrine system in animals. When SS is used to immunize animals, the correspondingly generated anti-SS antibody neutralizes the SS and, therefore, alleviates its growth inhibiting effects. This is of great value to the livestock industry; however, previously developed methods fail to obtain enough recombinant SS in an economical way. Herein, we describe the employment of a commonly used feed enzyme, i.e., xylanase, as a carrier protein for recombinant expression of SS in large quantity. The SS gene was fused to one of the two xylanase genes (XynCDBFV and BsXynC) and recombinantly expressed in Pichia pastoris. The purified xylanase-SS fusion proteins displayed excellent antigenicity and immunogenicity. In addition, they retained the enzymatic activities and thermostability of the xylanases, indicating that they can catalyze hydrolysis of xylan in plant cell wall of the animal feeds and stand the high temperature in feed pelleting. Thus, the xylanase-SS fusion proteins serve as an excellent candidate chimeric bifunctional vaccine-feed enzyme protein retaining both SS immunogenicity and xylanase activity. KEY POINTS: • Somatostatin is expressed in P. pastoris as fusion proteins with two xylanases. • The chimeric proteins retain both immunogenicity and xylanase activity. • The xylanase-SS proteins may serve as bifunctional proteins in livestock industry.